We mine gold and diamonds because of greed -- we actually do a lot of things (like go to work) because of greed.There is a coin that solves the prime number problem (primecoin) as proof of work. Prime numbers are important in Cryptography. If you can come up with something, it's possible straightforward to issue a new coin with that proof of work function. Maybe SETI would be interested in their own coin? Also understand that the work done provides the security of the token. If it's easy to do, the blockchain is less secure. This makes it the cost of having a trustless token.